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.Dd September 12, 2019
.Dt MAT_REWIND 3
.Os
.Sh NAME
.Nm Mat_Rewind
.Nd Rewinds an open MAT file to the beginning.
.Sh SYNOPSIS
.Fd #include <matio.h>
.Ft int
.Fo Mat_Rewind
.Fa "mat_t *matfp"
.Fc
.Sh DESCRIPTION
Rewinds an open MAT file so that
.Fn Mat_VarReadNext
or
.Fn Mat_VarReadNextInfo
reads the first variable in the file.
.Sh RETURN VALUES
The function returns 0 on success, or -1 on failure.
.Sh EXAMPLES
The following example shows a list of variables in the MAT file, and prompts the
user for the index of the variable to read.
If the index is valid, the file is
reset to the beginning, and variables read until the selected index is reached.
.Bd -literal
#include <stdlib.h>
#include <stdio.h>
#include "matio.h"

int
main(int argc, char **argv)
{
    mat_t    *matfp;
    matvar_t *matvar;
    int       idx, num_variables;

    matfp = Mat_Open(argv[1], MAT_ACC_RDONLY);
    if ( NULL == matfp ) {
        fprintf(stderr, "Error opening MAT file %s\n", argv[1]);
        return EXIT_FAILURE;
    }

    idx = 0;
    while ( NULL != (matvar = Mat_VarReadNextInfo(matfp)) ) {
        idx++;
        printf("%3d. %s\n", idx, matvar->name);
        Mat_VarFree(matvar);
    }
    num_variables = idx;
    if ( num_variables > 0 ) {
        printf("Which variable would you like to read? ");
        if ( 0 == fscanf(stdin,"%d",&idx) ) {
            printf("Invalid variable selection!\n");
        } else if ( idx < 1 || idx > num_variables ) {
            fprintf(stderr, "That is an invalid variable index!\n");
        } else {
            int k;
            Mat_Rewind(matfp);
            for ( k = 1; k < idx; k++ ) {
                matvar = Mat_VarReadNextInfo(matfp);
                Mat_VarFree(matvar);
            }
            matvar = Mat_VarReadNext(matfp);
            Mat_VarPrint(matvar, 1);
            Mat_VarFree(matvar);
        }
    }

    Mat_Close(matfp);
    return EXIT_SUCCESS;
}
.Ed
.Sh SEE ALSO
.Xr Mat_Open 3 ,
.Xr Mat_Close 3 ,
.Xr Mat_VarReadNext 3 ,
.Xr Mat_VarReadNextInfo 3 ,
.Xr Mat_VarPrint 3
